Edward Creutz Was Indeed a Distinguished Pioneer of the Nuclear Era
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NATIONAL ACADEMY OF SCIENCES EDWARD CHESTER CREUTZ 1 9 1 3 – 2 0 0 9 A Biographical Memoir by GEORGE HINMAN AND D A V I D R OSE Any opinions expressed in this memoir are those of the authors and do not necessarily reflect the views of the National Academy of Sciences. Biographical Memoir COPYRIGHT 2010 NATIONAL ACADEMY OF SCIENCES WASHINGTON, D.C. EDWARD CHESTER CREUTZ January 23, 1913–June 27, 2009 BY GEORGE HINMAN AND DAVID ROSE DWARD CREUTZ BEGAN HIS PROFESSIONAL CAREER at a historic Etime. He arrived at Princeton University in 1939 when World War II was beginning and physicists were just learning about nuclear fission. Both events greatly affected his early years. As the national security implications of nuclear fission became clear, his initial research at Princeton shifted from nuclear interactions and radioactive decay to the properties of chain-reacting piles and nuclear explosives. His experimental work at Princeton and later at the University of Chicago and Los Alamos was fundamental to the development of pluto- nium production reactors and plutonium-based explosives. For a brief period from 1942 to 1945 he joined much of the nation’s nuclear physics community in the Manhattan Project, the remarkable effort that led to the end of World War II. After the war, he left Los Alamos and continued a career that included prominent positions in academia, the nuclear industry, the federal government, and a private museum. Throughout his career he continued to lecture and publish on a wide range of topics in physics, metallurgy, biology, science education, and science policy. Ed was born in Beaver Dam, Wisconsin, on January 23, 1913, during a snowstorm, he says in his anticipatory obituary.1 His father, Lester Creutz, was a high school history teacher 3 4 B IOGRA P HICAL MEMOIRS and later a school administrator, and his mother, Grace Smith Creutz, taught general science before the birth of his older brothers, John and Jim. The family moved from Beaver Dam to Eau Claire, then to Monroe, and finally to Janesville, Wisconsin, as his father advanced in the public school system. Ed’s sister, Edith, was born in Eau Claire. They were very close as children and remained so in later life. As would be expected, Ed liked mathematics and science subjects in school, but he also pursued many interests outside the classroom during his elementary and high school years. In high school he taught himself to play the banjo, left handed, and later added the mandolin, ukulele, percussion instruments, and trombone. He played base drum in the high school band, tympani and banjo in the orchestra, and tenor banjo in Rosie’s Ragadors, whose members performed at local dances and other events. He went out for football and played left guard on the high school teams in Monroe and Janesville. He was proud of the fact that in Monroe he played every minute of every game. Ed was especially interested in biology in his early years. He collected insects and reptiles and read widely in the field. He developed a strong interest in color photography, experimented with nearly all the processes known at the time, and developed his own process using black and white printing paper but adding color with heavy metal salts. He continued work on this subject in later years. When he graduated from high school, Ed did not proceed to college right away. He took a job as bookkeeper in a local bank in Janesville in order to help with the family finances—his two brothers were in college at the time.I n the fall of 1932 his brother John convinced him to go to college, and he entered the University of Wisconsin at Madison. He considered majors in botany, geology, and chemistry but decided on physics when John told him that it was basic for E DWARD CHESTER CREUTZ 5 the other sciences. He progressed through the physics curric- ulum and became acquainted with his instructors, several of whom became lifelong friends and colleagues. His freshman course professor was Julian Mack, who introduced him to research by giving him a small research project to do during his freshman year. One of us (G.W.H.) remembers when, 20 years later, Ed invited Mack to General Atomic at San Diego as a consultant. Ed gave him a small tool kit and invited him to get to work just as Julian had done for him so many years before. Other influential faculty at Madison were Ragnar (“Rollie”) Rollefson, his junior physics instructor; Raymond Herb, who helped him develop important research skills; Gregory Breit, his Ph.D. dissertation sponsor; and especially Eugene Wigner, who inspired and guided much of his early work. It was during this period that he developed many of the skills that served him well as an experimental physicist. As a senior thesis he built and used equipment to separate the two isotopes of lithium, although no thesis was required for graduation. He received B.S. degrees in mathematics and in physics in 1936. Ed remained at Wisconsin for graduate work He was increasingly drawn to the new field of nuclear physics and worked on Ray Herb’s project to upgrade the proton energy of the department’s Van de Graaff generator from 300 KeV to 600 KeV. The improvement provided enough energy for him to undertake as his dissertation a suggestion by Gregory Breit to study resonance scattering of protons from lithium at a narrow 440 KeV resonance, where previous investigations had shown that proton bombardment produced high-energy gamma rays. The mechanism responsible for the gamma rays was unknown and was of considerable interest at the time. Ed’s measurements showed that the gamma rays arose from direct decay of a virtual level of the compound nucleus 8Be and not from an excited alpha particle produced after double 6 B IOGRA P HICAL MEMOIRS alpha particle decay of the level (1939). It also was during this graduate student period that he met Lela Rollefson, Rollie’s sister, who was a mathematics student at the time. They married on September 13, 1937. Lela was interested in science, and for a number of years at Wisconsin and Princeton she helped Ed with data collection and analysis. He includes acknowledgements of her assistance in publica- tions from that period. By the time Ed was in graduate school he had established himself as a valuable and skillful experimenter who was able to get things done. Eugene Wigner moved from Wisconsin to Princeton in 1938, and Ed soon received an offer of a posi- tion there. The University of California had given Princeton a 36 inch magnet, which the Physics Department used to construct an 8 MeV proton cyclotron. The department hired Ed to help get the cyclotron into operation. He moved to Princeton and joined the research group working with the new machine. Ed loved to tell the following anecdote about one of his early experiences at Princeton: On my third day at Princeton, I was invited to give a short report on my thesis. There usually were two or three speakers at these “Journal Club”’ meetings. This time the speakers were Niels Bohr, Albert Einstein, and Ed Creutz! To be on the same program with these two giants of scientific accomplishment was breathtaking. Just before the meeting began, my sponsor, Delsasso, asked me, “Say Creutz, have you met Einstein yet?” I had not. Delsasso took me over to where Einstein was sitting in sweatshirt and tennis shoes and said, “Professor Einstein, this is Creutz, who has come to work on our cyclotron.” The great man held out his hand, which seemed as big as a dinner plate, and said in an accented voice, “I’m glad to meet you, Dr. Creutz.” I managed to wheeze out, “I’m glad to meet you too, Dr. Einstein.” Life went on, but not in the same way. Bohr had brought to the meeting the details of the discovery of the fission of uranium, an entirely unexpected development in physics. E DWARD CHESTER CREUTZ 7 In the period from 1939 to 1941 Ed worked with other members of the Physics Department at Princeton on projects that led to 19 journal papers on experimental techniques and nuclear experiments. The most extensive set of experiments, carried out with M. G. White, L. A. Delsasso, and others, dealt with light “Wigner” nuclei, each of which contains a number of neutrons exceeding by one the number of protons. When such a nucleus is bombarded with energetic protons, it can through a (p,n) reaction be converted to a nucleus whose proton number exceeds by one the neutron number. Wigner had pointed out that if the neutron-neutron nuclear force and the proton-proton nuclear force are equal, the energy difference between the original and product nucleus should be approximately equal to the difference in the Coulomb energy of the two. This difference could be determined by measuring the endpoint energy of the positrons emitted by the product nucleus. The results of the Princeton group’s work on eight of these nuclei, combined with similar work elsewhere on four others, showed good agreement with expectations (1941). By 1941 the discovery of nuclear fission, and especially its neutron multiplication property, was claiming the attention of nuclear physicists. While there was general interest in the physics of the process, many physicists already realized its weapons potential. Leo Szilard, Edward Teller, and Eugene Wigner had already, two years before, composed a letter to President Roosevelt, actually signed by Albert Einstein, pointing out that Germany might develop a powerful new bomb based on the process and urging that work on this subject should be undertaken in the United States.